Abstract: Jizhong depression is rich in oil-gas resources. After more than 40 years of exploration and development, it has been the main oil-gas production base and a crucial area for increasing reserves and production in Huabei oilfield. In recent years, multiple important breakthroughs have been made in new fields and new types of hydrocarbon exploration, showing good exploration prospects. However, it still faces problems such as unclear understanding of hydrocarbon accumulation conditions, as well as undetermined replacement areas and plays. Based on systematically analyzing the hydrocarbon accumulation conditions and their controlling factors in Jizhong depression, the paper summarizes the oil-gas enrichment regularities, recognizes the hydrocarbon accumulation characteristics and exploration potentials of the depression, and further points out the prospects and directions for new fields and new types of future exploration in the depression. Comprehensive assessment indicates that Jizhong depression has developed the Paleogene and Carboniferous-Permian source beds, forming two main reservoirs including marine carbonate rocks and Paleogene clastic rocks. Moreover, it has four types of hydrocarbon plays, i.e., new-generation and paleo-reservoir, self-generation and self-reservoir, lower generation and upper reservoir, paleo-generation and paleo-reservoir, constituting four types of composite hydrocarbon accumulation belts dominated by paleo-buried hills, i.e., central uplift, steep slope, slope, and trough, for which the proved rates of oil-gas resources are 45.7% and 11.0% respectively, and where the remaining hydrocarbon resources are abundant. The holistic research suggests that the five major fields of deep buried-hills and their inners, deep Paleogene layers, shale oil, deep coalbed methane, and new sags generally have good accumulation conditions, great resource potentials, and broad exploration prospects. Thirteen favorable targets, as favorable plays for natural gas exploration in Jizhong depression, have been implemented in the buried-hills and inners, such as Hexiwu buried-hill of Langgu sag, Wuqing sag, and Wen'an slope in northern Jizhong depression, with the predicted natural gas resources of 1 453×10⁸m³. Twelve favorable structures, as the main plays for the exploration of deep Paleogene layers in Jizhong depression, are developed in the Liuchu-Huangfucun area of Raoyang sag, Wuqing anticline belt of Wuqing sag, Yuke-Shennan anticline belt of Shenxian sag, inner belt of Wen'an slope, Langgu sag, and steep slope of Jinxian sag, with the predicted oil resources of 2.4×10⁸t. The predicted trap resources of 2.3×10⁸t in two favorable tectonic belts in Baoding sag and the remaining natural gas resources of 836×10⁸m³ in Wuqing sag demonstrate that they are realistic areas achieving exploration breakthroughs in new wellblocks of sags. The available shale oil resources in the lower submember of Member 3 of Shahejie Formation in Shulu sag and the lower submember of Member 1 of Shahejie Formation in Raoyang sag are estimated to be 9.1×10⁸t, and the total resources of the favorable exploration area for deep coalbed methane in the outer blet of Wen'an slope amount to 1.53×10¹²m³, indicating the favorable exploration targets for strategic replacement in unconventional fields in Jizhong depression.

Key words: Jizhong depression, accumulation condition, deep buried-hill and inner, shale oil, coalbed methane, new sag, exploration direction

摘要： 冀中坳陷油气资源丰富，历经40余年勘探开发，是华北油田的主要油气生产基地和增储上产的重要战场。近年来，冀中坳陷的油气勘探在新领域、新类型取得了多项重要突破，展现出良好的勘探前景，但仍面临着油气成藏条件认识不清、规模接替领域和区带不明的问题。基于对冀中坳陷油气成藏条件的系统解剖，通过分析油气成藏的控制因素，总结油气富集规律，重新认识了坳陷的油气成藏特征与勘探潜力，指出了冀中坳陷在今后一个时期的勘探新领域、新类型。综合评价认为，冀中坳陷发育古近系和石炭系—二叠系2套烃源层，形成海相碳酸盐岩和古近系碎屑岩2种主要储集体，具备新生古储、自生自储、下生上储、古生古储4类成藏组合，构成了以古潜山为主体的中央隆起型、陡坡型、斜坡型和洼槽型4种复式油气聚集带。冀中坳陷石油与天然气资源的探明率分别为45.7%和11.0%，剩余油气资源十分丰富。整体研究认为，深潜山及其内幕、古近系深层、页岩油、深部煤层气、新凹陷5大领域的整体成藏条件好，资源潜力大，勘探前景广阔。冀中坳陷北部在廊固凹陷河西务潜山、武清凹陷和文安斜坡等潜山及内幕落实了13个有利目标，预测天然气圈闭资源量为1 453×10⁸m³，是冀中坳陷天然气勘探的有利区带；在饶阳凹陷留楚—皇甫村、武清凹陷武清背斜带、深县凹陷榆科—深南背斜带、文安斜坡内带、廊固凹陷和晋县凹陷陡坡带等地区发育12个有利构造，预测石油圈闭资源量为2.4×10⁸t，是冀中坳陷古近系深层领域勘探的主攻区带；保定凹陷在2个有利构造区的预测圈闭资源量为2.3×10⁸t、武清凹陷的剩余天然气资源量达836×10⁸m³，是凹陷新区勘探突破的现实地区；束鹿凹陷沙河街组三段下亚段和饶阳凹陷沙河街组一段下亚段的页岩油可动资源量为9.1×10⁸t，文安斜坡外带深部煤层气有利勘探区的总资源量为1.53×10¹²m³，是冀中坳陷非常规领域战略接替的有利勘探目标。

关键词: 冀中坳陷, 成藏条件, 深潜山及内幕, 页岩油, 煤层气, 新凹陷, 勘探方向